Development of Codoped Cesium Iodide Scintillators for Medical Imaging Applications

Cesium iodide has a rich history of use as a scintillating material. CsI finds use in a variety of fields, but it is primarily used in radiography, tomography, and geological exploration. Of the three common variants of CsI, thallium doped CsI is by far the most widely used among these applications. It possesses favorable physical characteristics like a high density and high effective Z and exhibits high light output at room temperature. Despite how great CsI scintillators may be on paper, they have an Achilles heel: afterglow. CsI:Tl has significant afterglow which leads to imaging artifacts that can be difficult to correct. Therefore, the scintillation research community has made a considerable effort to find a way to reduce afterglow. It was found that codoping with very small amounts of divalent cations reduced the afterglow of CsI:Tl substantially. Such successes with altering the scintillation properties of CsI:Tl raises the question as to whether other CsI scintillators may be improved by codoping. In this thesis, the effects of divalent cation codoping on the scintillation properties of cesium iodide doped with sodium (CsI:Na) are explored.